Vapor operated ejector vacuum pump



K- C. D- HICKMAN VAPOR OPERATED EJECTOR VACUUM PUMP June 24, 1958 3 Sheets-Sheet 1 Filed June 5, 1953 June 24, 1958 K. c. D. HICKMAN VAPOR OPERATED EJECTOR VACUUM PUMP Filed June 5, 1953 3 Sheets-Sheet 3 2,840,297 Patented June 24, 1958 VAPOR OPERATED EJECTOR VACUUM PUMP Kenneth C. D. Hickman, Rochester, N. Y., assignor, by mesne assignments, to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of Cal.- fornia Application June 5, 1953, Serial No. 359,824

16 Claims. (Cl. 230-101) This invention relates to vapor operated ejector vacuum pumps and has particular reference to certain new and useful improvements therein designed to improve the efllciency thereof and to permit the pump to be shut down instantly and to be maintained in a prewarmed state so that it can be restarted instantly.

The type of pump that has found greatest favor as a secondary pump for producing high vacuum with relatively large throughput is a vapor entrainment device consisting of a vertical standpipe situated concentrically in a tall vertical pot fitted with a side arm towards the lower end. The standpipe is perforated with one or more rings of holes at suitable positions and skirts are fastened around these to form one or more jets for vapor. The pump further includes a heater associated with the base for heating a relatively involatile liquid which may be mercury or a heavy oil contained in the bottom of the pot. Vacuum Technique, by Arnold L. Reimann, published by Chapman & Hall Ltd., London, 1952, contains an excellent review of pumps of this type.

The present invention relates to pumps of this character in which the working fluid may be mercury'or a heavy oil, and the improvements herein disclosed provide special advantages in pumps operated with liquids other than mercury as such liquids are more or less thermally unstable.

Pumps of this type as now employed are subject to a number of drawbacks. In the first place, they cannot be conveniently shut down without waiting for the pump and the working fluid to cool. In the second place, they cannot be maintained in a prewarmed or standby state 'so as to be ready to function at the instant that forevacuum is applied, thus necessitating a long starting period. In addition, in such pumps the heat is delivered first to the casing, then to the working fluid, and thence to the standpipe and jets. The jets never fully reach the evaporating temperature and vapor condenses in the standpipe which could usefully be employed in pumping. The oil furthermore has to carry the double thermal load of heating the pump and of producing more vapor than required. Furthermore, whenever the fore-vacuum is broken, evaporation ceases and the temperature of the charge rises, and if a labile oil is being used as the working fluid, this oilwill be damaged if not completely spoiled.

According to my invention, all of the foregoing drawbacks are eliminated by the features hereinafter disclosed which are simple in character and which greatly increase the utility of the pump and simplify the manipulation and control thereof.

A principal object of the invention therefore is to provide a novel and improved vapor operated ejector vacuum pump.

Another object of the invention is to provide in a pump of the character described provisions for efiiciently and rapidly dissociating and associating the working fluid and the heater so as to permit the operation of the pump to be stopped and started during the operation of the 2 V heater and without reducing the rate at which heat is supplied by the heater to the pump (other than the working fluid).

Another object of the invention is to provide a pump of the character described with novel and more efiicient heating means.

Other and further objects of the invention will be apparent from the following description and claims and .may be understood by reference to the accompanying drawings, of which there are three sheets, which by way of illustration show preferred embodiments of the invention and what I now consider to be the best mode in which I have contemplated applying the principles of my invention. Other embodiments of the invention may be used without departing from the scope of. the present invention as set forth in the appended claims.

In the drawings:

Fig. 1 is a vertical sectional somewhat diagrammatic view of one form of a pump embodying my invention;

Fig. 2 is a horizontal sectional view taken along the line 22 of Fig. 1;

Fig. 3 is a vertical sectional somewhat diagrammatic view of a pump illustrating a modification of my inventron;

Fig. 4 is a vertical sectional somewhat diagrammatic view of a further modification;

Fig. 5 is a fragmentary vertical sectional somewhat diagrammatic view showing a modification of Fig. 4;

Fig. 6 is a vertical sectional somewhat diagrammatic view of a further modification of my invention; and

Figs. 7 and 8 are vertical sectional somewhat diagrammatic views of further modifications of my invention.

. Referring now to Fig. l, thereis shown one form of a pump embodying my invention and which in general comprises a vertical glass pot 10 provided with a side arm 12 toward its lower end, the side arm being adapted for connection with a pump for producing fore-vacuum, as is common in the art. The upper end of the pot 10 is adapted for connection with the space to be evacuated. A standpipe 14 in the form of an aluminum tube is suitably arranged in the pot 10 as shown, concentrically disposed with respect to the innerwall of the pot 10. A suitable working fluid 16 of the types hereinbefore referred to or any other suitable type is placed in the bottom of the pot 10 to about the level indicated, sufficient fluid being used to make the pump operable. The standpipe is provided with a series of rings of holes 18, 2t) and 22, and skirts 24, 26, 28 and 30 are disposed around the standpipe to form downwardly directed vapor jets 32, 34 and 36. It will be understood that the pump may be provided with one or more jets and that the number or the specific construction thereof forms no part of the present invention.

A long coil of suitably insulated resistance wire 38 is wound in contact or close association with the standpipe 14, on either the inside or the outside thereof, although the disposition of the coil on the inside of the standpipe 14, as shown in Fig. 1, has constructional advantages when skirts are fitted to the outside of the standpipe as shown. The density of winding of the coil is adjusted to provide a greater input of heat toward the base. Preferably, I employ a resistance wire of a high thermal coeflicient of resistance, such as nickel wire. The leads 40 for the coil 38 pass through suitable openings in the Wall of the pot 10 and are sealed thereto. A cupshaped sleeve 42 isfitted around the base of the standpipe 14 so as to provide a space or reservoir 44 outside the standpipe 14. The outer periphery of the sleeve 42 is spaced from the inner wallof the pot 10 so as to permit the return of vapor which condenses on the inner wall of the pot 10 to the body thereof in the bottom of 3. the pot,and the bottom of the sleeve 42 and of the standpipe 14 are spaced from the bottom of the pot so as to permit the flow of liquid to the interior of the standpipe 14. A sleeve 46 of insulating material may surround the lower end of the standpipe 14 so as to insulate the liquid in the reservoir from the standpipe 14. The leads 40 are connected to a suitable source of 1 current whereby the coil 38 may be energized, and as is known, any suitable thermostatic or other type of control may be associated with the coil 38 for automatically and/or manually regulating the heat output thereof.

After the interior of the pot is placed under forevacuum and the coil 38 is energized, the liquid 16' within the standpipe 14 will be heated, as will the standpipe 14,

and vapor generated by the heating of such liquid and heated as. it is conducted through the standpipe 14 will issue slightly overheated from the jets 32, 34 and 36. This slight .superheating has several advantages.

densate hanging on the rims of the jets. Third, the vapor is accelerated with a greater velocity and is thus more able to effectpumping. Fourth, since there is no condensate in the standpipe, thejcomposition of the vapor is not altered after the initial act of evaporation, with a resulting higher vacuum.

Any suitable or conventional means maybe applied to the exterior of the pot 10 for cooling the same.

The pump is now in a steady operational state. Discontinuance of the application of fore-vacuum to the interior of the pot 10, either intentionally or accidentally as by bleeding air into the pot 10, will permit the pressure in the pot 10 torise above the normal working rangeof I pressure therein, thereby abruptly discontinuing the evaporation of the fluid 16 in the standpipe 14 and permitting the temperature thereof to rise. Since only part of the heat generated bythe coil 38 is applied directly to the liquid 16, the rise of temperature of such liquid is thereby limited, and is also limited by the thermal characteristic of the electric coil 38. Most of the heat generated by the coil will be dissipated from the standpipe to the casing or pot 10. In addition, the admission of air to the pot will cause most, if not all, of the liquid in the standpipe 14 to be drawn into the reservoir 44, the upper part of which has been evacuated in any suitable manner, and since the liquid in the reservoir 44 is thermally insulated from the coil 38, the rise of temperature of such liquid in the reservoir 44 will be limited. sulation 46 may be omitted and the lower end of the standpipe may be provided with a series of holes at different elevations, as shown in Fig. 4, so as to permit liquid from the reservoir to pass directly and freely into the standpipe 14 without flowing under the lower edge thereof.

If the current supplied to the heating coil is not discontinued, the coil will continue to heat the pump so as to maintain the same in a prewarmed state so that the instant that fore-vacuum is applied, the jet pump will immediately begin operating without waiting for the usual warm-up period. In this way the pump can be shut down instantly without waiting for the pump or the liquid to cool, the pump can be maintained in a prewarmed condition indefinitely if the heating coil 38 is not deenergized, and the operation of the pump can be resumed instantly upon the application of fore-vacuum to the interior of the pot. In cases Where labile liquids are employed the arrangement as described will prevent the rapid deterioration thereof, and in addition the liquid stored in the reservoir will be shielded from atmosphere.

In the modification shown in Fig. 3, the principle is the same but the construction is slightly different, and the reservoir is disposed outside the pot. In this case the pot 110 is provided with the side arm 112 for con- In some cases the in- A nection to the source of fore-vacuum. The standpipe 114 is enlarged as indicated at 115 at its lower end, but the outer periphery of the enlargement 115 is spaced from the inner wall of the pot 110 to permit the return of condensate to the working fluid 116 in the bottom of the pot. A heating coil 138, like the coil 38, is coiled and distributed inside the standpipe 114 as described with reference to coil 38 and standpipe 14. The standpipe is provided with two series of holes 122 and lZO which cooperate with the skirts 124 and 126 to define downwardly directed jets inside the pot 110. The reservoir 144 which comprises a closed evacuated vessel is connected by conduit 145 and flexible coupling 147 to a pipe 149 which communicates with the bottom of the pot 110. A cord 150 connected at one end to the reservoir 144 and at its other end to a hook 152 carried on the upper end of the pot 110 normally maintains the reservoir 144 above the normal level of the liquid 116 in the bottom of the pot 110.

The coil 138 will heat the liquid 116 and the standpipe 114 and effect the discharge of vapor from the jets 132 and 134 into the pot 110 when fore-vacuum is applied thereto. Upon rise in pressure in the pot 110 above the normal pressure range therein, as by the discontinuance of fore-vacuum to the interior of the pot, the liquid 116 in the bottom of the pot 110 will be forced through the connections 149, 147 and 145 into the reservoir 144 and thereby moved out of range of the heating element 138. If the heating element 138 is maintained energized, the liquid will be returned to the bottom of the pot 110 upon the application of fore-vacuum thereto and the pump Will instantly begin operating. The arrangement as disclosed in Fig. 3 will work in the same way as that disclosed in Fig. l, and in addition with the arrangement as disclosed in Fig. 3 the liquid may be removed from the pot 110 without regard to the pressure conditions therein merely byldisengaging the cord 150 from the hook 152 and lowering the reservoir below the level of the pot 110. The flexible coupling 147 permits this manipulation of the reservoir 144 so that gravity will cause the liquid to flow from the pot 110 to the reservoir 144 or vice versa, depending upon the relative elevation thereof.

The reservoir 144 may also be adjusted with respect to the bottom of the pot so as to regulate the amount of working fluid in the pump. The cord 150 is provided with a loop at its upper end but it may consist merely of a long string which can be wound around the hook 152 so as to maintain the reservoir 144 in any desired elevation.

With the arrangement as shown in Fig. 3, the liquid in the reservoir 144 is completely thermally dissociated from the heating element 138, whereas in Fig. l the liquid in the reservoir 44 is dissociated from the heating element 38 to the extent that it is moved to a relatively cooler region Where it can be maintained at a temperature sufiiciently low to discontinue the operation of the pump but without permitting the liquid to completely cool. Obviously, the degree of cooling obtained in Fig. 1 will be dependent to some extent upon the size of the reservoir and the efliciency of the insulation 46.

In the arrangement as shown in Fig. 4, the operation and construction are essentially the same as in Fig. 1, except that'in the case of Fig. 4 the reservoir 244 is arranged in the upper part of the pot 210 and is connected and supported by a tube 249 which extends downwardly through the standpipe 214 to a point below the liquid level in the bottom of the pot 210. In this case the heating coil 238 may be the same as the coil 38 and arranged in the same manner within the standpipe 214. The lower end of the standpipe is surrounded by an inverted cup-shaped sleeve 242, the outer periphery of whichis spaced slightly from the inner wall of the pot 210 so as to permit the return of fluid which condenses in the pot 210 to the body thereof in the lower end thereof. The'standpipe 214is provided with several series of .holes' 239 in the lower-. end thereof topermit liquid toflow freely from within the shell 242 into the tube 214 in addition; to the flow of liquid into the tube 214 through the lower open end thereof.

Fig. 4 also includes heat transfer fins 241 on the outside of the standpipe 214 tofaeilitate the flow of heat into the liquid .216in the bottom of; the pot. This modification also includes a diffuser 251 made of high thermally conducting metal to concentrate the vapors and to convey heat to the casing 210. A cooling'coil 211 isrshown in heat transfer relation with theo'utside of the pot 210 and the outside of the side arm 212. The construction and operation of the modification as illustrated in Fig. 4 are otherwise the same as previously described in connection with Fig. l. h

It is to be understood that in lieu of the specific-heating means illustrated in any of the modifications, any other known or desirable heating arrangementmaybe employed, although I have ,found the construction and arrangement disclosed to be particularly efiicacious for the reasons heretofore stated.

In the modification disclosed inFig. 5, which is a modification of that shown in Fig. 4, in lieu of the reservoir 244 .above the standpipe I provide the bottom-of the p0t310 with anexpansible bellows-like section 311 which as shown is in its collapsedposition. The bellowslike section 311 forms the bottom of the pot 310 and when collapsed as shown maintains the liquid level in the bottom of the pot 310 at a suificient elevation therein so that energizationofthe heating coil .338 will generate vapor from the liquid 316 and causethe .sameto flow upwardlythrough the standpipe 314 and, to be discharged from jets (as pe'rFig. 4) when fore-vacuum is applied to theinterior. of thepot 310. V 7

However, when the application offore-vacuum to the interior of the pot'3 is discontinued, the bellows-like section 311 will expand and thereby, drop the liquid 316 out ofcontact with the heating element 338and the standpipe 314, thereby discontinuing the evolution of vapors from the liquid 316, and as a result of this the operation of. the pump will be discontinued. Re-applicanon of fore-vacuum tothe interior 'of the pot 3I0will collapse the bellows-like section 311 to the positionas" shown in Fig. 5 and restore the liquid in the pot 310 to its normal level so asjto immediately eflfect the operation of the jet pump. I 1

The modification shown'in Fig. 6 is quite similar to that shown in Fig. 4, but is made of metal for ease of construction. -In Fig. 6 the casing or pet 410 may be made from a piece of thintubeconstricted at 411 to accommodate the standpipe 414 which is made of thermally conductive metal and is coveredat its top by a cap 419 whichforms a downwardly directed jet 432. "The liquid withdrawal reservoir 444 is attached to and supported by a vertical pipe 449 which passes downwardly through the cap 419 and the standpipe 41 4 and terminates at the bottom of the standpipe below'theliquid level therein. An insulated electrical resistance heating element 438, which may be of nickel wire, is applied to the outside of the constricted portion 413 of the casing. The standpipe 414 is provided with holes 415 to permit return of condensate from the interior of the casing 410. An internal helical spring 417 may be inserted in the lower end of the standpipe 414 to spread the evaporating pump liquid. The construction and operation of this modification are otherwise the same as described in connection with Fig. 4.

Fig. 7 is a modification of the arrangement illustrated in Fig. 5 and ditfers therefrom by reason of the fact that the standpipe and heating element are constructed and arranged so as to be movable in and out of the liquid in the bottom of the pot 510 for dissociating and associating the heating element and working fluid. As shown in Fig. 7, the pot 510 is provided with liquid 516 in the bot- 6 tom thereof and with the side arm 512 for attachment to the fore-vacuum producing means. is mounted. for vertical reciprocation within the pot 510 and concentrically thereof. A bellows 511 suspended from a bar 513 which extends across the topof the pot 510 has aifixed to its lower end a cap 519 and the standpipe 514, the cap 519 cooperating with holes in the upper end of the standpipe to define a downwardly directed jet 532.

An electrical resistance heating element 538 of the kind previously referred to is coiled within and in contact with the standpipe 514, the lower end of the standpipe depending during operation of the pump into the liquid 516 in the bottom of the pot.

The bellows 511 comprises a pressure responsive device which under the influence of the fore-vacuum applied to the interior of the pot 510 will lower the standpipe 514 and the heating element carried thereby into the liquid 516 so as to effect the evolution of vapors from the liquid 516 and the discharge of the same through thejet 532 downwardly into the pot 510. A spring 515 isincorpo'rated in the bellows 511 so that when the application of fore-vacuum to the interior of the pot 510 is discontinued, the spring 515 will elevate the standpipe 514 and the heating element 538 carried thereby out of the working liquid 516, therebyv discontinuing the operation of the pump automatically upon cessation of the fore-vacuum. Re-application of fore-vacuum to the interior of the pot will expand the bellows 511 and thereby automatically operatively associate the heating element 538' in heat exchange relation with the wall of the generator 639 so as to heat the liquid 616 therein. A heated tube 614, which functions somewhat as a standpipe, conducts the vapors to the jet 632 which is arranged in a conicalshaped passage or chamber 633. One end 635 of the chamber 633'is adapted for connection to the space to be evacuated while the other end is provided with a nipple 612 for connection to a source of fore-vacuum. The vapors condensed in the chamber 633 are returned through the conduit 637 to the lower end of the generator 639. A conduit. 649, a flexible coupling 647, and a pipe 645 connect thebottom end of the generator 639 with the reservoir 644 which is the same as that shown in Fig. 3. In this case a portion of the coil 638 may be coiled around the standpipe 614 so as to heat the vapors in their passage through the same to the jet 632, and the chamber 633 may be provided with a water-cooled heat exchanger 640.

The modification disclosed in Fig. 8 will operate in essentially the same way as that disclosed in Fig. 3 so far as my invention is concerned, the difference consisting principally in the fact that the type of pump disclosed in Fig. 8 is different from that shown in Fig. 3. It will be understood that suitable lagging or insulation may be applied to any of the foregoing modifications for the purpose of retarding the dissipation of heat therefrom or the absorption of heat thereby or by difierent parts thereof.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

The standpipe 514 I claim! 1. In a vaponoperated ejector pump having a jet, a pot for containinga poo1 of liquid, means for heating the pot for containing a pool of liquid, means in the pump adjacent-the pool for heating the liquid of the pool to vaporize it,.and a conduit connecting the pot to the jet forfeeding the resulting vapor to the jet, the combination which comprises a reservoir connected to the pot below the level of the pool of liquid therein, and automatic means for forcing theliquid of the pool into thereservoir when the pressure in the pump increases above a predetermined level and for forcing the liquid back from the reservoir into the pool when the pressure in the pump decreases to avaluebelow said level.

3. Apparatus according to claim 2 in which the reservoir is an annular chamber disposed in the pot around the conduit.

4. Apparatus according to claim 2 in which the reservoir is disposed above the pool of liquid in the pot and is provided with a second conduit disposed within the first conduit and connected to the reservoir and with its lower end projecting into the pool.

5. Apparatus according to claim 2 in which the reservoir is movable .up and down with respect to the bottom heating means disposed in the pump adjacent the pool,

the heating means and pool being movable withrespect to each other, a control chamber disposed to have its internal pressure afiected by the pressure within the pump, and means responsive. to the pressure differential between the pump interior'and the chamber interior to move the pool and heating means farther apart when the pressure within the pump increases and to move the pool andheating means closer together when the pressure within the pump decreases.

8. Apparatus according to claim 7 in which the position of the pool is substantially fixed and the heating means is movable.

9. Apparatus according to claim 7 in which the heating means is fixed and the upper surface of the pool is movable up and down. i

10. In a vapor-operated ejector pump having a pot 8 for containing a pool of liquid to be vaporized and a jet through which the resulting vapor is forced, the combination which comprises a conduit having an upper portion connected. to the jet with its lower portion project- 'ing into the pool, the lower portion being movable up and down with respect to the pool, heating means mounted on the lower portion of the conduit, a control chamber disposed to have its internal pressure affected by the pressure within the pump, and means responsive to the pressure differential between the pump interior and the chamber interior for moving the lower portion of the conduit and the heating means carried thereby up and down with respect to the pool.

11.Apparatus according to claim 10 in which the means for moving the conduit and the heating means up and down is a pressure-responsive bellows disposed inside the pump.

12. In a vapor-operated ejector pump having a jet and a pot for containing a pool of liquid to be vaporized and forced through the jet, the combination which comprises a conduit connected to the jet and carrying it, the conduit being movable up and down and having its lower end disposed in the pool of liquid, heating means mounted on the conduit and movable therewith, a control chamber disposed to have its internal pressure affected by the pressure within the pump, and means responsive to the pressure differential between the pump interior and the chamber interior for moving the conduit andthe jet and heating means carried thereon up and down with respect to the pool.

13. A vapor-operated ejector pump comprising a pot, a pool of liquid to be vaporized in the pot, a movable standpipe of high heat conductivity extending upwardly in the pot with its lower end immersed in the pool, a jet through which 'the resulting vapor is ejected connected to an upper portion of the standpipe, and a heating element attached to and disposed against the standpipe and projecting above the pool in intimate thermal conductive References Cited in the tile of this patent UNITED STATES PATENTS 1,471,661 Houskeeper Oct. 23, 1923 2,386,298 Downing Oct. 9, 1945 2,464,369 Baxter Mar. 15, 1949 FOREIGN PATENTS Germany July 10, 1925 

